Generally, CRTs are designed to reproduce picture images on a panel screen by exciting phosphors, coated on the screen, with electron beams emitting from an electron gun and passing through apertures of a color-selecting shadow mask.
The shadow mask ensures that each electron beam lands on the correct phosphor. The shadow mask is welded to a shadow mask frame connected to stud pins embedded into a side wall of the panel by interposing springs therebetween.
The shadow mask comprises a very thin metal plate having a plurality of beam-guide apertures, and is extremely susceptible to vibration even at a minimal shock or impact from the external, or a sound wave from a built-in speaker. During such a vibration, electron beams deviate from their correct courses and land on inappropriate phosphors or black matrix portions, deteriorating color purity.
In order to overcome the aforementioned problem, various proposals have been made. For example, the welding position of the spring and the shadow mask frame, or the coupling position of the spring and the stud pin is changed to stop vibration in the transmitting course of the stud pin, the spring and the mask frame. However, such type of technique cannot be well adapted to coping with various vibration sources and amplitudes.
In contrast, it is also proposed to minimize vibration of the shadow mask by strengthening the rigidity thereof. However, this technique involves a difficult forming process, resulting in high production cost.